In oil and gas production, scaling in the production fluid flow creates in part great problems and requires costly measures for the conveying capacity of the pipeline to be maintained. The scaling is formed by crystallized substances entrained in the production fluid, for example carbonates, being deposited on surfaces in the pipeline. It is common knowledge that the scaling occurs in particular in turbulent areas and in dead-water zones, that it to say in areas where the geometry brings about a reduced flow rate. This is due to the fact that the scaling intensity is governed by two mutually counteracting processes, namely a) electrochemical forces pulling the crystals towards the pipeline surfaces and b) the fluid flow pulling on the crystals. In zones with vigorous fluid flow, the flow-induced forces are dominant so that scaling is prevented, whereas the electrochemical forces are dominant where the fluid flow is reduced, which may result in scaling.
It is therefore an advantage if a pipeline creates dead-water zones to the least possible degree, for example by there being, to the least possible degree, sharp restrictions that create turbulent flow with adjacent stagnant fluid. Even if this is known to a person skilled in the art, pipelines will often be provided with such critical restrictions, especially in connection with valves. In addition to the fact that scaling at a valve affects the conveying capacity of the pipeline, scaling at a valve may, moreover, affect the ability of the valve to shut off the fluid flow, and, at worst, scaling in the valve may lead to the valve becoming inoperative. This may particularly apply to valves that are very rarely readjusted. A dead-water zone appears in particular downstream of the restriction, on the lee side, that is. FIG. 1 illustrates a simulation of flow velocity around the lee side of a restriction, that is to say downstream of the restriction.